1. Field of the Invention
The invention, generally, relates to packaging techniques for printed circuit boards and, more particularly, to a technique for mixing various wiring technologies with various cross section thicknesses in the same printed circuit board.
Today, it is common throughout industry to use separate printed circuit boards for each function to be performed within a particular system. This practice has developed largely due to cost and performance factors, since different functions require different cross section and wiring technologies.
The practice that is common today does not permit the degree of flexibility in circuit construction and arrangement that cost and performance packaging requires. Input/Output circuits alone require performance considerations that lower cost connectors do not provide.
An example of the trend that is prevalent today is to construct printed circuit boards of several electrically conductive layers with alternate layers of a dielectric material. Interconnections between layers are provided by vias that are coated with electrically conductive material, such as copper.
It has been found that use of a multilayered structure for a printed circuit board provides substantial flexibility, particularly in supercomputer environments. Connections between the respective electrical circuits and components still must be accomplished by using conductive vias.
2. Description of the Prior Art
U.S. Pat. No. 3,436,819 to Lunine describes a multilayer laminate circuit board having various circuit configurations on different planes with a method of making interconnections at the various planes for internal operations and for contact to the surface of the multilayer laminate.
U.S. Patent No. 3,516,156 to Steranko describes electrical voltage packaging technique which permits an electrical voltage on one or more planes buried within the package to be brought out to the surface of the package with a connection insulated from the intervening layers.
U.S. Pat. No. 4,659,931 to Schmitz et al. discloses a multilayered module formed of thin film non-conductive layers as well as layers having conductive patterns arranged to effect electrical connections between devices and to the surface of the module as an electrical interconnect system.
U.S. Pat. No. 5,012,047 to Dohya describes a multilayer wiring substrate with signal layers on the top and bottom connected together and to selected internal layers by vias so that the external layers function as bonding pads for connecting leads and as lands for Input/Output pins.
While these prior arrangements may be effective for their stated purposes, what is needed today is a packaging technique that will permit multiple wiring cross sections combined in a multiple cross section structure. It is to this end that the present invention is directed. Moreover, when the packaging technique of the invention is utilized as will be described in detail presently, it provides other advantages not available and not even contemplated by the prior arrangements.